Double Pipe Heat Exchanger

A double pipe heat exchanger, in its simplest emergence is just one pipe inside another larger pipe. One fluid flows all the way through the surrounded by pipe and the additional flows throughout the annulus stuck between the two pipes. The wall of the inner pipe is the heat transfer surface. The pipes are usually doubled back multiple times as shown in the diagram at the left, in order to make the overall unit more compact. The term 'hairpin heat exchanger' is also used for a heat exchanger of the configuration in the diagram. A hairpin heat exchanger may have only one inside pipe, or it may have multiple inside tubes, but it will always have the doubling back feature shown. . Some heat exchanger manufacturers advertise the availability of finned tubes in a hairpin or double pipe heat exchanger. These would always be longitudinal fins, rather than the more common radial fins used in a cross flow finned tube heat exchanger.